Process for imparting improved latent crimp to filaments



United States Patent 3,224,068 PROCESS FOR IMPARTING IMPROVED LATENTCRIMP TO FHLAMENTS Robert Alexander Edington, George Edward Barlow, and

Peter Bernard Checkland, Harrogate, England, assignors to ImperialChemical Industries Limited, London, England, a corporation of GreatBritain No Drawing. Fiied May 15, 1963, Ser. No. 280,724 Claimspriority, application Great Britain, May 24, 1962, 20,046/ 62 5 Claims.(Cl. 28-72) The present invention relates to an improved device formaking potentially crimped or crimped synthetic linear polymerfilaments.

In our British Patent 808,213 is described a process and apparatus formaking potentially crimped continuous synthetic polymer filaments byheating the moving filaments non-uniformly while passing over a narrowsurface heated to a temperature above the melting temperature of thefilaments in such a way that the filaments are heated on one side onlycontinuously along their length, while under a tension to give a stablestretch to the filaments of not more than The latent crimp in thepotentially crimped filaments is brought out by relaxing the filamentsby subjecting them to a heat treatment while they are under a free orcontrolled tension which permits free or controlled shrinkage.

The narrow surface disclosed in the specification of British Patent808,213 was an electrically heated wire, pin or bar. The heating wasaffected by the resistance of the wire, pin or bar and was ratherdifiicult to control. The path over which each filament passed wascooled by the passage of the filament and when filament strayed slightlyfrom its path it was subjected to uneven heat until the new path hadbeen cooled. In the process described in the specification of BritishPatent 808,213 the wire was heated to red heat, and the filament pathscooled to black heat with the passage of the filaments.

We have now discovered that the process described in British Patent808,213 is improved if the heated narrow surface is provided on anindirectly heated member. The yarn produced by the improved process isof the same character as the yarn produced by the earlier process, butis more uniform, having a greater regularity of bulk along its length.

According to the present invention, in a process for making potentiallycrimped continuous thermoplastic synthetic linear polymer filaments byheating moving continuous filaments non-uniformly while passing over anarrow surface heated to a temperature above the melting temperature ofthe filaments in such a way that the filaments are uniformly heated onone side only continuously along their length, wherein the heated narrowsurface is provided on an indirectly heated member.

The latent crimp in the potentially crimped filaments is brought outwhen the filaments are heated and relaxed, preferably at a temperatureabove the second order transition temperature of the filaments and atleast C. below the melt temperature of the filaments. This heattreatment may be carried out whilst the filaments are under a free orcontrolled tension which permits free or controlled shrinkage, and maybe carried out by hot inert fluids, for example, or by contact with aheated surface.

Further according to the present invention we provide apparatus forcarrying out the improved process.

The surface-providing member is preferably made of an abrasion-resistantheat-conducting material, such for example as tungsten, molybdenumtungsten carbide or ceramic material.

Alternatively, the member may be formed of softer metal, such as iron,brass or aluminium, having an outer layer of the abrasion-resistantmaterial which provides the narrow surface.

The indirectly heated member may be in thermal contact with a heatedbody or may be heated indirectly by radiated heat. The heated body canbe heated by a heating element, by electrical induction or resistance,by high frequency induction or by heat exchange with a heated fluid,which may be circulated from or may surround a suitable heat source.

A thermal sensing device may be arranged near or to in contact with theindirectly heated member, preferably on or close to the surfacecontacted by the moving filaments, in order to measure and/or controlthe temperature attained by the metal strip or bar.

In operation the yarn is preferably passed over a ribbon forming devicewhich may take the form of a convex surface terminating near to, but notin contact with, the heated narrow surface. The etfect of this ribbonforming device is to spread the filaments of the yarn substantially intothe form of a ribbon in which the filaments are continually reshufiiingand passing over one another. The ribbon forming guide may be made ofmild steel provided with sand blasted and satin chromed finish, hardenedsteel or alloys, solid ceramics or metals with ceramic or other hardenedcoatings. It should be effectively heat insulated from the heated narrowsurface so that the temperature of the ribbon forming guide never risessubstantially, being limited to approximately C. in operation.

Preferably, the ribbon of filaments approach the leading edge of theheated narrow surface at an angle between 1 and 20 to the surface.Similarly, the potentially crimped yarn leaves the heated narrow surfaceat an angle between 1 and 20, not necessarily the same as the angle ofincidence.

In a preferred form, the indirectly heated member is provided as a metalstrip and the heated narrow surface provided on it is substantiallyflat, although the entry to the surface may be modified in the interestsof operating efficiency. For example, modifying the approach edge of thestrip and adjusting the angle of incidence of the yarn to the narrowsurface and the angle of leaving can give increased production rateswhen using the process.

After a period of operation, the passage of filaments can wear groovesin the narrow surface parallel to the mean filament path but these, farfrom having a deleterious effect, may assist the uniformity of theproduct and such grooves may be produced advantageously in the virginnarrow surface.

Crimped yarn when produced by our invention consists of a bundle ofindividual filaments, each of which is crimped along its length, butcrimped in such a way that examination of a length of a single filamentreveals a range of crimp amplitude and frequency; this range is suchthat over intermittent lengths the filaments may be substantiallyuncrimped. The yarn itself consists of a bundle of such filaments inwhich the ditferent crimp amplitudes and frequencies in the individualfilaments are substantially out of phase from one filament to another.Thus, if the yarn bundle is examined at any point along its length itwill consist of filaments which, at the point of examination, show fromone filament to another, a range of crimp amplitude and frequency, someperhaps showing substantially no crimp at all. Individual filaments mayequally show a variation in crimp along their lengths, parts havinggreater or lesser crimp or even no crimp at all. The maximum frequencywill depend on the temperature of the narrow surface, the polymerforming the filaments, the rate of passage over the heated narrowsurface, i.e. the effective dwell time, and the denier of the filaments.Crunodal loops are rare and there is no tendency for the crimps to existpreferentially in the yarn surface.

The improved process of the present invention is subject to the samevariation of modifications of details as the invention described andclaimed in the specification of British Patent 808,213.

The filaments are preferably passed over the heated narrow surface at aspeed between 100 and 1,000 metres per minute. The process of theinvention may be preceded by a drawing process, preferably to extend theasspun length of the filaments at least three times, and followed bywinding-up. The improved process may be incorporated in a spin-drawprocess, after drawing, when the filaments are under a small tension tostretch them not more than 10% The process of the present invention canbe carried out when the filaments are wetted, for example with alubricant spin finished solution.

The filaments produced by the present invention may be cut into thestaple fibres and this can be done before or after the latent crimp isbrought out by heating and relaxing. Equally, the heating and relaxingtreatment may be carried out after the potentially crimped filamentshave been woven or knitted into textile articles.

Preferred embodiments of the invention will now be described in furtherdetail by way of examples:

Example I A sample of #144 filament polyethylene terephthalate yarn ismelt spun and after being lubricated with a finish consisting of anaqueous dispersion of an oil, is wound up as undrawn yarn of 810 denier.It is drawn to 3.6 times its original length at a speed of 450 yds./min.and passed over the heated surface of a strip of tungsten 0030 widewhich is maintained at 370 C. by contact with a metal block containing a50 watt electrical heating element. Also clamped to the block is aribbon forming guide in the shape of a 90 segment of a cylinder whichassists in spreading the filaments into a ribbon. The ribbon formingguide is thermally insulated from the metal block so that itstemperature does not rise above 100 C. The filaments when passing overthe strip of tungsten are deflected by about 5 and are under sufficienttension to ensure good contact, but the tension causes a stretch of lessthan The yarn is then allowed to relax in a hot air system in which theair is at a temperature of 200 C. In this hot air Zone the yarn suffersa contractlon of 24%. The product is a bulky yarn similar to yarns madeby the process described in British Patent 808,213, consisting of abundle of filaments in which diiferent crimp amplitudes and crimpfrequencies in individual filaments are substantially out of phase fromone filament to another. The denier 0f the yarn remains substantiallyunchanged under loads up to 50 gms. and the single or plied yarn issuitable for end uses where bulky fabrics are required. It can be madeinto acceptable knitted and woven fabrics.

Example II A sample of 540 denier, 48 filament, polyethyleneterephthalate melt spun yarn is drawn as in Example I, but at a speed of750 ft./min. and passed over a tungsten strip 0.025" wide, heated to atemperature of 365 C. indirectly by contact with a metal blockcontaining a 50 watt heater. The yarn is then relaxed in hot air at 205C. by being overfed into a tube through which hot air circulates, theratio of feed speed to final wind-up speed being 1.43: 1. The product,which is wound up on a cheese, is a crimped yarn containing filamentsexhibiting a range of crimp amplitude and frequency and whose denier isunaffected by loads up to 45 gms. Examination of the yarn shows thatcrunodal loops are rare and there is no tendency for the crimps to existpreferentially in the yarn surface. The yarn may be knitted or woveninto fabrics having considerably greater bulk than fabrics made fromnormal filament yarns.

4 Example III A sample of 36 filament polyethylene terephthalate yarn ismelt spun and after being lubricated with a finish consisting of anaqueous dispersion of an oil is wound up as undrawn yarn of 360 denier.It is drawn to 3.2 times its original length at a speed of 1250'ft./min. and passed over the heated surface of a strip of tungstencarbide containing 6% cobalt, the strip being 0.030 wide and having arectangular profile with the approach edge ground back at an angle of 30to the surface :over which the filaments run for a depth of 0.0 20". Thestrip is maintained at 370 C. by contact with a metal block containing athermostatted 50 watt electrical heating element. Clamped adjacent tothe block is a ribbon forming guide in the shape of a 160 segment of acylinder over of which the yarn passes to be spread substantially intothe form of a ribbon. The ribbon forming guide is thermally insulatedfrom the metal block so that its temperature does not rise above C. inoperation. The filaments when passing over the strip of tungsten aredeflected by about 10 and are under sufficient tension to ensure goodcontact. The yarn leaving the strip is then allowed to relax in a hotair system in which the air is at a temperature of 210 C. In this hotair zone the yarn suifers a contraction of 28%. The product is a bulkyyarn similar to those made by the process described in British Patent808,213 consisting of a bundle of filaments in which different crimpamplitudes and crimp frequencies in individual filaments aresubstantially out of phase from one filament to another The denier ofthe yarn remains substantially unchanged under loads up to 40 gms. andthe single or plied yarn is suitable for end uses where bulky fabricsare required.

Example IV Undrawn nylon 66 yarn of 210 denier was triple plied and colddrawn through a draw ratio of 3.0 to 1 at a speed of 800 ft./min. andpassed over the heated surface of a strip of tungsten 0.030" wide whichwas maintained at a temperature of 350 C. by contact with a metal blockcontaining a thermostatted 50 watt electric heater. The yarn was thenoverfed into a tube through which hot air at a temperature of 205 C. wascirculating. The ratio of feed speed to final wind-up speed was 1.2to 1. The product, which was wound on a cheese package, was a crimpedyarn containing filaments exhibiting a range of crimp amplitude andfrequency in individual filaments and substantially out of phase fromone filament to another. The product was suitable for knitting orweaving and showed a resistance to tension in excess of that normallyexhibited in bulked yarns manufactured by false twist methods.

Example V A sample of 72 filament 360 denier polyethylene terephthalatemelt spun yarn is drawn as in Example III at a speed of 1250 ft./min.and passed over satin-chrome plated curved guide having an arc ofcontact of 90 which spreads the filaments of the yarn substantially intothe form of a ribbon. The yarn then passes over a tungsten strip spread4" from the end of the curved guide, approaching the strip at an angleof 10 to the surface of the strip over which the yarn passes and leavingat an angle of 5 to said surface so that the yarn is held against saidsurface. The approach edge of the strip is shaped to a radius of 0.005"and the surface over which the yarn passes is grooved parallel to theyarn path, the grooves being spaced at 1500 per inch and 0.0005 indepth. The strip is heated indirectly and maintained at a temperature of375 C. by contact with a metal block containing a 50 watt cartridgeheating element which is thermostatically controlled. The curved guideis insulated from the tungsten strip and the heated block and maintainsa temperature of 60 C. when the yarn is running.

The yarn leaving the tungsten strip is allowed to relax in hot air at205 C. and the relaxation causes the yarn to suffer a 25% contraction.

The final product is a bulky yarn similar to that made in the .processdescribed in British Patent 808,213 but of improved quality in that ithas a better handle and the crimp is in general more uniform.

Example VI A sample of 48 filament 480 denier polyethylene terephthalateyarn is spun and drawn as in Example III but at a speed of 825 feet perminute. After passing through an arc of contact of 90 C. over a curvedribbon-forming guide it passes over a tungsten strip located from theend of the curved guide and heated indirectly to 365 C. by contact witha metal block containing a 50 watt cartridge heating element. Thesurface of the tungsten strip over which the yarn passes is inclined at15 so that the angle of the approach edge is 105 and the angle of theleaving edge is 75. The yarn approaches the surface of the tungstenstrip at an angle of 5 to the surface and leaves at an angle of to thesurface, giving a deflection of by which the yarn is held against thesurface.

The curved guide, which is insulated, maintains a temperature of 62 C.when the yarn is running.

The yarn leaving the tungsten strip is overfed at a ratio of 1.4 to 1into a hot air system in which the air is at a temperature of 205 C.

The final product is a bulky yarn, similar to the products of BritishPatent 808,213, having crimp frequencies ranging from zero to a highestlocal value of 140 crimps per inch, but having an improved uniformityand a more pleasing handle.

In general, the products of the present invention, when compared withthe products of British Patent 808,2113 show the same essentialcharacteristics in that the crimp has the random nature described in theabove examples, but is generally more uniform, has a greater regularityof bulk along its length, and, when woven or knitted,

6 produces fabrics of more uniform appearance and better handle.

What we claim is:

1. A process for improving imparting of a latent crimp to continuoussynthetic linear polymer filaments which on relaxing will have moreuniformity and will have a greater regularity of bulk along the lengthof said filaments comprising passing continuous synthetic linear polymerfilaments over a narrow surface indirectly heated to a temperature abovethe melting temperature of said filaments in such a manner that saidfilaments are uniformly heated on one side only continuously along theirlength.

2. The process of claim 1 wherein the filaments after passing over thenarrow surface are relaxed to bring out the latent crimp of saidfilaments.

3. The process of claim 2 wherein the filaments after passing over thenarrow surface are heated and relaxed at under controlled tension at atemperature above the second order transition temperature of thefilaments and below the melt temperature of the filaments whereby thelatent crimp is brought out.

4. The process of claim 3 wherein the filaments are made of polyethyleneterephthalate.

5. The process of claim 3 wherein the filaments are made of nylon.

References Cited by the Examiner UNITED STATES PATENTS 1,330,534 2/1920Hertel et a1. 28-72 2,919,534 1/1960 Boliuger et al 28-72 3,017,6841/1962 Pittman 28-72 3,025,584 3/1962 Evans 28-72 3,112,551 12/1963Schmieder et al. 28-72 FOREIGN PATENTS 600,877 6/ 1960 Canada. 808,2131/ 1959 Great Britain.

DONALD W. PARKER, Primary Examiner.

RUSSELL C. MADER, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,224,068 December 21, 1965 Robert Alexander Edington et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 12, for "0.020 read 0.002 column 6, line 18, for "aunder" read under a Signed and sealed this 18th day of October 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A PROCESS FOR IMPROVING IMPARTING OF A LATENT CRIMP TO CONTINUOUSSYNTHETIC LINEAR POLYMER FILAMENTS WHICH ON RELAXING WILL HAVE MOREUNIFORMITY AND WILL HAVE A GREATER REGULARITY OF BULK ALONG THE LENGTHOF SAID FILAMENTS COMPRISING PASSING CONTINUOUS SYNTHETIC LINEAR POLYMERFILAMENTS OVER A NARROW SURFACE INDIRECTLY HEATED TO A TEMPERATURE ABOVETHE MELTING TEMPERATURE OF SAID FILAMENTS IN SUCH A MANNER THAT SAIDFILAMENTS ARE UNIFORMLY HEATED ON ONE SIDE CONTINUOUSLY ALONG THEIRLENGTH.